RE: ammonia. Let the cigars age. That's the only way to get rid of it. Also, open up your humi at least once per week for an air exchange if you have young cigars. An airtight humi (like a tupperdore) will make the ammonia problem worse.
RE: beetles. They hatch if your humi gets too warm. I would never intentially use humidification with an insecticide, b/c it has to be some sort of chemical, but that's a personal preference. Your best bet is to buy good cigars, from a reliable source. You could also freeze all cigars for 3 days upon arrival, though some say that the home freezer does not get cold enough to kill the eggs.
JMHO